1. Field of the Invention
The invention relates to hand-held material dispensing devices such as caulking guns.
2. Description of the Related Art
Hand-held material dispensing devices are well known in the art and generally rely on the action of a piston to push fluid out of a receptacle towards the application area. The motion of the piston is induced by the advancement of a piston rod in the direction of the receptacle, with the piston rod being advanced in the direction of travel by the operator's squeezing of a trigger in engagement therewith.
One such dispenser is shown in U.S. Pat. No. 3,140,078 to Krahe et al. The device of Krahe does not utilize a trigger, and is not concerned with biasing the piston rod in the forward direction.
Another fluid dispenser is disclosed in U.S. Pat. No. 4,461,407 to Finnegan. The Finnegan patent incorporates an automatic pressure release mechanism, but fails to address the forward biasing concerns with which the instant patent is concerned.
In U.S. Pat. No. 4,081,112 to Chang, there is disclosed a caulking gun having a forward-biasing spring to urge the trigger back to the cocked position after an application cycle. However, Chang does not make provisions for biasing the piston rod in the forward direction.
U.S. Pat. No. 4,033,484 to Ornsteen shows a hot melt adhesive gun which operates in the conventional manner of the prior art. However, the Ornsteen patent also fails to provide a forward-biasing mechanism for the piston rod to maintain contact of the piston with the fluid receptacle.
U.S. Pat. No. 3,069,053 to Nilsson and U.S. Pat. No. 3,189,226 to Sherbondy each show a caulking gun with an alternative piston rod-trigger engagement arrangement. In these patented guns the trigger urges the piston rod toward the fluid receptacle by means by a ratchet mechanism. They do not, however, make provisions for biasing the piston rod in the forward direction when the trigger is not in operation.